c o r t e x x x x ( 2 0 1 5 ) 1 e2
Available online at www.sciencedirect.com
ScienceDirect Journal homepage: www.elsevier.com/locate/cortex
Clinical Postcard
Dissociated word production and comprehension in semantic dementia Julie S. Snowden a,b,* a b
Cerebral Function Unit, Greater Manchester Neuroscience Centre, Salford Royal NHS Foundation Trust, Salford, UK Institute of Brain Behaviour and Mental Health, University of Manchester, Manchester, UK
Mr H has semantic dementia, a progressive disorder of conceptual knowledge associated with degeneration of the anterior temporal lobes. Like many other people with the condition he is chatty and sociable. During his clinic visit he remarked “we're going shopping in Manchester when we leave here”. As he was about to leave, I said to him “So you're going to Manchester now, are you?” He looked blank and asked “What's Manchester?” He had no comprehension. Mr H was exhibiting a phenomenon that we observe from time to time in people with semantic dementia: they might use a word appropriately in the course of their conversation yet fail to recognise that same word subsequently when it is used by others. What is the context of this apparent anomaly? Mr H has a nine year progressive difficulty of naming and understanding words, beginning at 63 years. At initial referral, two years prior to his current visit he exhibited a severe yet circumscribed semantic disorder. He scored 0/30 on the Graded naming test (McKenna & Warrington, 1983) and performed at chance level on the Pyramids and Palm trees test of semantic association (Howard & Patterson, 1992). He performed well on perceptual and spatial tasks (Visual Object and Spatial Perception battery (Warrington & James, 1991): Screening test 20/20, Incomplete letters 19/20, Dot counting 10/10, position discrimination 20/ 20; number location 10/10, cube analysis 10/10) except where they made semantic demands (Silhouettes 1/30). Performance on the Brixton spatial anticipation test (Burgess & Shallice, 1997) was in the high average range. A CT scan showed severe bilateral temporal lobe atrophy. At the current clinic visit, he named 1/40 items on an undemanding picture naming test involving common animals, fruits and vegetables, articles of clothing and household objects (healthy control median score ¼ 40/40), and performed at chance level (8/40) on a four-
choice word-picture matching test using those same items. His conversational speech was fluent, effortless and grammatically correct, but notable for a paucity of substantive terms and for a tendency to focus on personally-related themes such as his favourite television programme. When he produced nouns, this was mainly in the course of describing daily activities: “I go out on my bike”, “I get my shoes. I put them on my feet”, although not exclusively so “Don't forget your keys” (when looking at a bunch of keys on the table). He was later, in the same clinic session, asked to name a key, a shoe, his feet and a picture of a bicycle. He could not do so. Anomalies observed in other patients are also in the context of severe semantic impairment. Mr L, after a 14-year history of gradual, systematic decline in semantic knowledge, showed floor level naming and word comprehension on formal tests. During a home visit, when presented with a picture to look at, he said “I'll just go and get my glasses”, which he duly did. Later, he was shown an array of objects which included his glasses, and he was asked to point to named items. He showed no comprehension of any of the object names, including the word “glasses”, nor could he name his glasses on confrontation. Mrs B, after an 8-year history of gradual decline in her ability to name and understand words and to recognise faces and objects, performed at floor level on formal tests of word comprehension and naming. On leaving a clinic room she said “I'll put on my coat”, which she did. She was later asked to point to objects in the room, including her coat. She showed no comprehension of any of the words including “coat”. Such disparities are intriguing because they occur against a background of high consistency of semantic performance.
* Cerebral Function Unit, Greater Manchester Neuroscience Centre, Salford Royal NHS Foundation Trust, Salford, UK. E-mail address: [email protected]. http://dx.doi.org/10.1016/j.cortex.2015.04.006 0010-9452/© 2015 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Snowden, J. S., Dissociated word production and comprehension in semantic dementia, Cortex (2015), http://dx.doi.org/10.1016/j.cortex.2015.04.006
2
c o r t e x x x x ( 2 0 1 5 ) 1 e2
The semantic impairment in Mr H, Mr L and Mrs B, as in other patients with semantic dementia, has prototypical characteristics of ‘semantic storage’ disorder (McCarthy & Warrington, 1994), and not one of refractory semantic access. Knowledge has become degraded in a systematic and predictable fashion, with no day-to-day variation in performance. Indeed, the disparity between Mr H's ability to name Manchester yet fail subsequently to understand the term seems all the more striking by virtue of the prevailing consistency of his semantic disorder. The basis for such dissociations between word production and comprehension in semantic dementia is open to speculation. Nevertheless, our impression is that dissociations are confined to words generated in patients' propositional speech, usually as part of an expressed action or intent: “I'll put on my coat”, “I'll just get my glasses”; “We're going shopping in Manchester”. Lack of comprehension occurs when the individual word “coat”, “glasses”, “Manchester” is stripped away from that very specific goal-directed context. Two decades ago we drew attention to the role of personal experience in influencing residual knowledge in patients with semantic dementia (Snowden, Griffiths, & Neary, 1994; 1995). A word or object might be understood only in the specific context in which it is encountered in daily life. Funnell (2001) framed these autobiographical effects in terms of script theory (Schank, 1982). She argued that meaning is represented on a continuum of levels of abstraction, with specific ‘event scripts’, derived from personal experience, representing the most context-bound level of meaning. We raise the possibility that Mr H's ability to convey, using pertinent vocabulary, his plan to going shopping in Manchester represents an example of preservation of an event script in the absence of understanding of abstracted words. Such an interpretation would
carry the implication that semantic memory cannot be fully understood solely with reference to single words and objects. It may encompass larger units of meaning that includes the goal-directed scripts of our daily lives.
references
Burgess, P. W., & Shallice, T. (1997). Hayling and brixton tests. Oxford: Pearson Assessment. Funnell, E. (2001). Evidence for scripts in semantic dementia: implications for theories of semantic memory. Cognitive Neuropsychology, 18(4), 323e341. Howard, D., & Patterson, K. (1992). Pyramids and palm trees: A test of semantic access from pictures and words. Oxford: Pearson Assessment. McCarthy, R. A., & Warrington, E. K. (1994). Disorders of semantic memory. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences, 346(1315), 89e96. McKenna, P., & Warrington, E. K. (1983). Graded naming test. Windsor, UK: NFER-Nelson. Schank, R. C. (1982). Dynamic memory. Cambridge: Cambridge University Press. Snowden, J. S., Griffiths, H., & Neary, D. (1994). Semantic dementia: autobiographical contribution to preservation of meaning. Cognitive Neuropsychology, 11(3), 265e288. Snowden, J. S., Griffiths, H. L., & Neary, D. (1995). Autobiographical experience and word meaning. Memory, 3(3e4), 225e246. Warrington, E. K., & James, M. (1991). The visual object and space perception battery. Oxford: Pearson Assessment.
Received 26 March Reviewed 27 March Revised 10 April Accepted 13 April
2015 2015 2015 2015
Please cite this article in press as: Snowden, J. S., Dissociated word production and comprehension in semantic dementia, Cortex (2015), http://dx.doi.org/10.1016/j.cortex.2015.04.006
Available online at www.sciencedirect.com
ScienceDirect Journal homepage: www.elsevier.com/locate/cortex
Clinical Postcard
Dissociated word production and comprehension in semantic dementia Julie S. Snowden a,b,* a b
Cerebral Function Unit, Greater Manchester Neuroscience Centre, Salford Royal NHS Foundation Trust, Salford, UK Institute of Brain Behaviour and Mental Health, University of Manchester, Manchester, UK
Mr H has semantic dementia, a progressive disorder of conceptual knowledge associated with degeneration of the anterior temporal lobes. Like many other people with the condition he is chatty and sociable. During his clinic visit he remarked “we're going shopping in Manchester when we leave here”. As he was about to leave, I said to him “So you're going to Manchester now, are you?” He looked blank and asked “What's Manchester?” He had no comprehension. Mr H was exhibiting a phenomenon that we observe from time to time in people with semantic dementia: they might use a word appropriately in the course of their conversation yet fail to recognise that same word subsequently when it is used by others. What is the context of this apparent anomaly? Mr H has a nine year progressive difficulty of naming and understanding words, beginning at 63 years. At initial referral, two years prior to his current visit he exhibited a severe yet circumscribed semantic disorder. He scored 0/30 on the Graded naming test (McKenna & Warrington, 1983) and performed at chance level on the Pyramids and Palm trees test of semantic association (Howard & Patterson, 1992). He performed well on perceptual and spatial tasks (Visual Object and Spatial Perception battery (Warrington & James, 1991): Screening test 20/20, Incomplete letters 19/20, Dot counting 10/10, position discrimination 20/ 20; number location 10/10, cube analysis 10/10) except where they made semantic demands (Silhouettes 1/30). Performance on the Brixton spatial anticipation test (Burgess & Shallice, 1997) was in the high average range. A CT scan showed severe bilateral temporal lobe atrophy. At the current clinic visit, he named 1/40 items on an undemanding picture naming test involving common animals, fruits and vegetables, articles of clothing and household objects (healthy control median score ¼ 40/40), and performed at chance level (8/40) on a four-
choice word-picture matching test using those same items. His conversational speech was fluent, effortless and grammatically correct, but notable for a paucity of substantive terms and for a tendency to focus on personally-related themes such as his favourite television programme. When he produced nouns, this was mainly in the course of describing daily activities: “I go out on my bike”, “I get my shoes. I put them on my feet”, although not exclusively so “Don't forget your keys” (when looking at a bunch of keys on the table). He was later, in the same clinic session, asked to name a key, a shoe, his feet and a picture of a bicycle. He could not do so. Anomalies observed in other patients are also in the context of severe semantic impairment. Mr L, after a 14-year history of gradual, systematic decline in semantic knowledge, showed floor level naming and word comprehension on formal tests. During a home visit, when presented with a picture to look at, he said “I'll just go and get my glasses”, which he duly did. Later, he was shown an array of objects which included his glasses, and he was asked to point to named items. He showed no comprehension of any of the object names, including the word “glasses”, nor could he name his glasses on confrontation. Mrs B, after an 8-year history of gradual decline in her ability to name and understand words and to recognise faces and objects, performed at floor level on formal tests of word comprehension and naming. On leaving a clinic room she said “I'll put on my coat”, which she did. She was later asked to point to objects in the room, including her coat. She showed no comprehension of any of the words including “coat”. Such disparities are intriguing because they occur against a background of high consistency of semantic performance.
* Cerebral Function Unit, Greater Manchester Neuroscience Centre, Salford Royal NHS Foundation Trust, Salford, UK. E-mail address: [email protected]. http://dx.doi.org/10.1016/j.cortex.2015.04.006 0010-9452/© 2015 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Snowden, J. S., Dissociated word production and comprehension in semantic dementia, Cortex (2015), http://dx.doi.org/10.1016/j.cortex.2015.04.006
2
c o r t e x x x x ( 2 0 1 5 ) 1 e2
The semantic impairment in Mr H, Mr L and Mrs B, as in other patients with semantic dementia, has prototypical characteristics of ‘semantic storage’ disorder (McCarthy & Warrington, 1994), and not one of refractory semantic access. Knowledge has become degraded in a systematic and predictable fashion, with no day-to-day variation in performance. Indeed, the disparity between Mr H's ability to name Manchester yet fail subsequently to understand the term seems all the more striking by virtue of the prevailing consistency of his semantic disorder. The basis for such dissociations between word production and comprehension in semantic dementia is open to speculation. Nevertheless, our impression is that dissociations are confined to words generated in patients' propositional speech, usually as part of an expressed action or intent: “I'll put on my coat”, “I'll just get my glasses”; “We're going shopping in Manchester”. Lack of comprehension occurs when the individual word “coat”, “glasses”, “Manchester” is stripped away from that very specific goal-directed context. Two decades ago we drew attention to the role of personal experience in influencing residual knowledge in patients with semantic dementia (Snowden, Griffiths, & Neary, 1994; 1995). A word or object might be understood only in the specific context in which it is encountered in daily life. Funnell (2001) framed these autobiographical effects in terms of script theory (Schank, 1982). She argued that meaning is represented on a continuum of levels of abstraction, with specific ‘event scripts’, derived from personal experience, representing the most context-bound level of meaning. We raise the possibility that Mr H's ability to convey, using pertinent vocabulary, his plan to going shopping in Manchester represents an example of preservation of an event script in the absence of understanding of abstracted words. Such an interpretation would
carry the implication that semantic memory cannot be fully understood solely with reference to single words and objects. It may encompass larger units of meaning that includes the goal-directed scripts of our daily lives.
references
Burgess, P. W., & Shallice, T. (1997). Hayling and brixton tests. Oxford: Pearson Assessment. Funnell, E. (2001). Evidence for scripts in semantic dementia: implications for theories of semantic memory. Cognitive Neuropsychology, 18(4), 323e341. Howard, D., & Patterson, K. (1992). Pyramids and palm trees: A test of semantic access from pictures and words. Oxford: Pearson Assessment. McCarthy, R. A., & Warrington, E. K. (1994). Disorders of semantic memory. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences, 346(1315), 89e96. McKenna, P., & Warrington, E. K. (1983). Graded naming test. Windsor, UK: NFER-Nelson. Schank, R. C. (1982). Dynamic memory. Cambridge: Cambridge University Press. Snowden, J. S., Griffiths, H., & Neary, D. (1994). Semantic dementia: autobiographical contribution to preservation of meaning. Cognitive Neuropsychology, 11(3), 265e288. Snowden, J. S., Griffiths, H. L., & Neary, D. (1995). Autobiographical experience and word meaning. Memory, 3(3e4), 225e246. Warrington, E. K., & James, M. (1991). The visual object and space perception battery. Oxford: Pearson Assessment.
Received 26 March Reviewed 27 March Revised 10 April Accepted 13 April
2015 2015 2015 2015
Please cite this article in press as: Snowden, J. S., Dissociated word production and comprehension in semantic dementia, Cortex (2015), http://dx.doi.org/10.1016/j.cortex.2015.04.006
